The invention relates to a drive system having a drive motor and, more particularly, to an improved drive system with at least one current regulator assigned to a drive motor, wherein a current regulator causes the semiconductor contact elements of an electronic power stage to be controlled as a function of a rotor-position sensor.
A drive system having a drive motor is disclosed in EP-A-0 261 540. In this system, the drive motor has at least one current regulator assigned which controls the semiconductor contact elements of an electronic power stage as a function of a rotor-position sensor. The electronic power stage is arranged downstream from the drive motor. The rotor-position sensor has a rotor part coupled to the drive motor and also has a number of magnetic poles corresponding to the number of poles of the drive motor. The current setpoint that is supplied to the current regulator is increased by overlapping an auxiliary voltage during the instant of commutation. The auxiliary voltage is required for adjusting the current setpoint within a separate winding that is mounted within the rotor of the motor. The separate winding could be the winding of a tachometer which is coupled to the motor rotor. A rotor-position sensor is provided in the disclosed drive system in order to control the positioning of the individual valves of the electronic power stage. It has been shown, however, that even in the case of great manufacturing precision, spatial shifts between the rotor-position sensor and the winding which generates the auxiliary voltage can arise. These shifts result in a shift in time of the auxiliary voltage, which is active in the commutation range, with regard to the actual instant of commutation. This causes irregularities in the torque characteristic.
Therefore, one of the problems that the invention addresses is to develop a drive system with a drive motor that eliminates these kinds of torque fluctuations caused by unavoidable manufacturing tolerances.